Production of ammonium dithiocarbamate



March 18, 1941. l w. HQHILL ETAL PRODUCTION OF' AMMONIUM DITHIOCARBAMATE Filed Aug. 25. 19:9

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Patented Mar. 18, 1941 UNITED STATES PATENT orrlcr.

PRODUCTION 0F AMMONIUM DITHIO CARBAMATE Application August 25, 1939, Serial No. 291,814

3 Claims.

The present invention relates to the production of ammonium dithiocarbamate through the reaction between .carbon bisullide and liquid ammo- The reaction between carbon bisuliide and gasecus lammonia in solvents such las ketones or ethyl alcohol results in the formation `of ammonium thiocarbonate, lammonium ithiocarbamate and ammonium thiocyanate. y Upon introducing the `ammonia gas into liquid carbon bi-suliide, the ammonium thiocarbonate crystals are the first formed, following which crystals of the ammonium dithiocarbamalte precipitate. The separation of these two products is not sharp and, hence, each is contaminated by the other. The former is favored by using concentrated solutions with excess ammonia `and moderat-e temperature-s of the order of to 40 C., the latter by dilute solutions with excess carbon bisulde and low temperatures of the order of 0 to 10 C.

Ammonium thiocyarralte remains in the solution, larger amounts resul-ting after long standing.

It has been discovered that When liquid carbon bisuliide is reacted with liquid ammonia yat temperatures ranging from -33 to 40 C., various proportions of ammonium dithiocarbamate, ammonium thiocyanate, and an unidentiiied yellow -compound containing S and N in the proportions `of 2:3 and having most likely 4an empirical formula corresponding to HsCzNaSz, :are formed. The higher temperatures vfavor the formation of ammonium thiocyanate, there being no substantial quantities of other compounds except H25 formed above 40. The lower temperatures, and particularly those from -33 to -22 C., favor the production of this yellow compound, which is substantially insoluble in liquid :ammonia and i-n ethyl ether.

It has been `determined that when this compound is permitted to stand at temperatures below 35 C. methyl ether or other organic liquids ysuch as alcohols, esters, liet-ones, hydrocarbons or the like to prevent sublimation of the solid product yet permitting ready escape of gases, a conversion of the yellow product to ammonium dithiocarbamate occurs with generation of some H2S and due to the insolubility of the former in the covering liquid, precipitation takes place almost immediately.

For instance, and as lindicated Ain the flow sheet, if liquid carbon bisulde 'and more than suici-ent liquid ammonia necessary to react therewith, are placed in yan open vessel and vigorously lagitated to prevent stratification, after one hour a slurry containing voluminous quantities of the yellow product are obtained. This yellow product, after having been ltered and washed with the liquid ammonia, if treated with an org-anic liquid such .as ethyl ether below 35 C., is converted to a white crystalline compound which separates from the liquid as a precipitate. After a suliicient length of time, the yellow compound is completely converted to this white crystalline substance and upon evaporation of the organic liquid, the former is obtained in a dry state.

The white crystalline compound was positively identified as ammonium dithiocarbamate by reason of its following properties:

On standing in air, it sublimes very slowly, leaving .a slight residue which responds qualitatively to the test for thiocyanate. In moist air, the :compound absorbs moisture and becomes lemon yellow in color. When warmed in air, it fuses .and gives off ammonia and hydrogen suliide, the residue showing the presence of thio- -cyanate and free sulfur. It is insoluble in ethyl ether, slightly soluble in liquid ammonia and readily soluble in walter. In the latter, yclear colorless solutions .are produced which are neutral or slightly acid to litmus. Lead acetate added to the neutral solution forms a faintly yellow, curdy precipitate. An excess of the solution decolorizes iodine solution while excess of the latter forms `a y-ellow precipitate. Excess ferrie chloride solution gives a bla-ck precipitate, while this reagent in the presence of excess solution gives a transient black precipitate with `decolorization of the ferrie chloride. Aqueous solutions acidified with HC1 showed the same results as above when reacted with lead acetate and iodine, while with ferrie chloride no black precipitate is formed, although the ferrie chloride is reduced.

'I'he ammonium dithiocarbamate thus produced analyzes 97% pure.

In an attempt to Speed -up the conversion of the yellow compound to ammonium dithiocarbam-ate, 5.2 grams was reiiuxed with 54.3 grams of ethyl ether for 11/2 hours at 35 C. During that time, H23 'and NH3 were evolved, a small amount of a pinkish white solid deposited in the condenser, while the yellow compound completely disappeared. The other then evaporated loil? at room temperature `and a residue of only .3 gr-am was recovered, which was mostly free sulfur, although a qualitative test showed the prese-nce of some thiocyanate. Consequently, the conversion of the yellow product of dithiocarbamate must take place `at temperatures lower than 35 C. at atmospheric pressures and these conditions are, therefore, preferred in carrying out our process.

In working with liquid ammonia in place of ammonia, gas, as a rea-etant with carbon bisulde, certain advantages will be apparent, such as the lack of necessity of using vessels having large volume together with pumps or the like usually required in bubbling a gas through the liquid and conveying the unreacted gas back to a receiver or circulator. The solvent is lalso eliminated.

While the invention has been described with particular reference to specc embodiments, it is to be understood that it is not to be limited thereto but is to .be construed broadly and restricted solely by :the scope of the appended claims.

We claim:

1. A method of producing ammonium dithiocarbamate which includes reacting liquid carbon bisulfide with liquid ammonia and converting the yellow product of the reaction to ammonium dithiocarbamate by permitting it to stand in contact with an organic liquid in which it is substantially insoluble, below 35 C.

2. 'Ihe method of claim 1 in which Ithe organic liquid is ethyl ether.

3. A method of lproducing ammonium dithiocarbamate which includes reacting liquid carbon bisulde and liquid ammonia at atmospheric pressures, ltering oi the yellow product contained, washing it with liquid ammonia and converting the washed product to dithiocarbamalte by permitting it to stand in cont-act with ethyl ether below 35 C. and then evaporating the excess ether.

WILLIAM H. HILL. DONOVAN J. SALLEY. 

